Rotary type regenerative heat exchanger

ABSTRACT

There is provided a rotary type regenerative heat exchanger which can effectively prevent an air bypass leak or a gas bypass leak. A rotary type regenerative heat exchanger of the present invention has a rotor ( 4 ) rotating around a central shaft ( 2 ), a heat accumulator ( 8 ) which is constructed in a manner that an air (A) of being a heated fluid and a gas (G) of being a heating fluid filled in the rotor alternately pass therethrough by a rotation of the rotor to repeat heat accumulation and radiation, and a housing provided so as to house the rotor. Further, the rotary type regenerative heat exchanger comprises: a branch pipe ( 41, 47, 55 ) for taking out a part of the heating fluid; a seal gas fan ( 42, 48, 56 ) for pressurizing the taken-out heating fluid to a predetermined pressure; and a seal gas introducing duct ( 46, 52 ) which is provided in the housing so as to introduce the pressurized heating fluid into a predetermined space formed between the rotor and the housing.

BACKGROUND OF THE INVENTION

The present invention relates to a rotary type regenerative heatexchanger, and in particular, to a rotary type regenerative heatexchanger which is applicable to a steam power plant, an internalcombustion engine or the like.

Conventionally, there has been known a rotary type regenerative heatexchanger which is called as an air heater for preheating a combustionair in a boiler or the like. A structure of the conventional rotary typeregenerative heat exchanger will be explained below with reference toFIG. 6 and FIG. 7.

As shown in FIG. 6, a rotary type regenerative heat exchanger 1 includesa cylindrical rotor 4 rotating around a central shaft 2, and a housing 6arranged so as to house the rotor 4. The rotor 4 is provided with a heataccumulator 8 which repeats accumulation and radiation. An upper portionof the housing is provided with an air outlet duct 10 at the right-handhalf portion, and a gas inlet duct 12 at the left-hand half portion. Onthe other hand, a lower portion of the housing 6 is provided with an airinlet duct 14 at the left-hand half portion, and a gas outlet duct 16 atthe right-hand half portion.

In the rotary type regenerative heat exchanger 1 thus constructed, whenthe rotor 4 rotates, the heat accumulator 8 is alternately exposed to anair A and a gas G, and then, repeats an operation of accumulating a heatof the gas and radiating it to the air A, and thereby, the heat of gas Gbeing recovered into the air A.

For example, in a steam power plant, the aforesaid rotary typeregenerative heat exchanger 1 is arranged as shown in FIG. 7. In FIG. 7,the air A, which is a combustion air supplied to a boiler 18, issupplied into the rotary type regenerative heat exchanger 1 by means ofa fan (not shown), and then, is supplied to the boiler 18 after thetemperature of air A rises by a heat exchange made by the rotary typeregenerative heat exchanger 1. A part of the gas G discharged from theboiler 18 is again returned to the boiler as a re-circulating gas GR bymeans of a circulating gas fan 20. On the other hand, the remainder ofthe gas G is supplied to the rotary type regenerative heat exchanger 1,and then, the temperature of the gas G is lowered by making a heatexchange with the air A. Thereafter, the gas G is supplied to a chimneystack (not shown) so as to be discharged to the atmosphere.

In the rotary type regenerative heat exchanger 1 shown in FIG. 7, aninlet air pressure (Pai), an outlet air pressure (Pao), an inlet gaspressure (Pgi) and an outlet gas pressure (Pgo) have the followingrelationship.

 Pai>Pao>Pgi>Pgo

As is evident from the above relationship, in the rotary typeregenerative heat exchanger 1, various leaks of the air A and the gas Gare generated by the difference in pressure between the air side and thegas side.

These leaks include the following leaks. More specifically, there are ahigh temperature radial leak (HRL) which is generated in an upper endface of the rotor 4 on the inlet and outlet of the air A and the gas G,a low temperature radial leak (LRL) which is generated in a lower endface of the rotor 4 (see FIG. 7), a post leak (PL) which is generatedaround the central shaft 2 of the inlet and outlet of the air A and thegas G, an air bypass leak (ABL) which bypasses a space between the rotor4 and the housing 6 on the air side, an gas bypass leak (GBL) whichbypasses a space between the rotor 4 and the housing 6 on the gas side(see FIG. 7), and an axial leak (AL) which flows from the air side tothe gas side in the space between the rotor 4 and the housing 6.

In order to reduce these leaks, as shown in FIG. 6, the conventionalrotary type regenerative heat exchanger 1 is provided with the followingseals at the rotor 4 side; more specifically, a radial seal 22 whichradially extends so as to seal a space between the air side and the gasside in the upper and lower end faces of the rotor 4, a rotor post seal24 which is located around the central shaft 2 of the inlet and outletof the air A and the gas G, a ring-like bypass seal 26 which is locatedon an outer peripheral edge on the upper and lower end faces of therotor 4, and an axial seal 28 which is vertically located at an outerperipheral portion of the rotor 4 so as to seal the air side and the gasside.

On the other hand, the conventional rotary type regenerative heatexchanger 1 is provided with the following seals at the housing 6 side;more specifically, a sector plate 30 which is located facing the upperand lower end faces of the rotor 4 so as to seal a space between the airside and the gas side in the upper and lower end faces of the rotor 4,and an axial plate 32 which is vertically located along an outerperipheral portion of the rotor 4 so as to seal the air side and the gasside.

In the conventional rotary type regenerative heat exchanger 1 having thestructure as described above, the radial seal 22, rotor post seal 24,bypass seal 26 and the axial seal 28, which are attached to the rotor 4,slidably move on the sector plate 30 and the axial plate 32 fixed to thehousing 6, and a leak has been prevented by a mechanical contact ofthese plates with seals. However, according to the aforesaid structuresuch that the leak is prevented by a mechanical contact, in the casewhere the rotor 4 thermally deforms, and then, a gap between the plateand the seal becomes a state different from a design value, there hasarisen a problem that sufficient seal effect is not obtained.

Further, as shown in FIG. 7, by a generation of the air bypass leak ABL,a low temperature air A on the inlet and a high temperature air A on theoutlet are mixed in the rotary type regenerative heat exchanger 1. As aresult, the temperature of air A on the outlet lowers as compared withthe case of no leak. For this reason, the temperature of the combustionair A supplied to the boiler 18; as a result, there has arisen a problemthat the heat efficiency of the boiler 18 is lowered by the decrement intemperature.

Moreover, as shown in FIG. 7, by a generation of the gas bypass leakGBL, the quantity of gas which is used as a heating fluid decreases inthe rotary type regenerative heat exchanger; as a result, there hasarisen a problem that the heat efficiency of the boiler 18 is lowered bythe decrement in quantity.

SUMMARY OF THE INVENTION

In view of such circumstances, the present invention has been made inorder to solve the aforesaid problems in the prior art. Therefore, anobject of the present invention is to provide a rotary type regenerativeheat exchanger which can effectively prevent an air bypass leak or a gasbypass leak.

Further, another object of the present invention is to provide a rotarytype regenerative heat exchanger which can effectively prevent an airbypass leak or a gas bypass leak, and can improve a heat efficiency of aboiler.

To achieve the above object, the present invention provides a rotarytype regenerative heat exchanger comprising:

a rotor rotating around a central shaft;

a heat accumulator which is constructed in a manner that a heated fluidand a heating fluid filled in the rotor alternately pass therethrough bya rotation of the rotor to repeat heat accumulation and radiation;

a housing provided so as to house the rotor;

take-out means for taking out a part of the heating fluid;

pressurizing means for pressurizing the taken-out heating fluid to apredetermined pressure; and

a pressurized fluid introducing passage which is provided in the housingso as to introduce the pressurized heating fluid into a predeterminedspace formed between the rotor and the housing.

In the rotary type regenerative heat exchanger thus constructedaccording to the present invention, the heated fluid and the heatingfluid alternately pass through the heat accumulator by the rotation ofthe rotor, and then, the heat accumulator repeats an operation ofaccumulating a heat of the heating fluid and radiating it to the heatedfluid, and thus, the heat of the heating fluid is recovered to theheated fluid. Further, a part of the heating fluid is taken out by meansof the take-out means, and then, the taken-out heating fluid ispressurized to a predetermined pressure, and thus, by means of thepressurized fluid introducing passage, the pressurized heating fluid isintroducing into a predetermined space between the rotor and thehousing. As a result, the pressure of the space becomes high; therefore,it is possible to effectively prevent an air bypass leak which hasconventionally generated.

In summary, the rotary type regenerative heat exchanger can effectivelyprevent an air bypass leak or a gas bypass leak, and can improve a healefficiency of the boiler.

In the present invention, the pressurized fluid introducing passage maybe provided on a heated fluid side of the housing, a heating fluid sideof the housing, or on both heated fluid side and heating fluid side ofthe housing.

In the present invention, the take-out means may branch and take out apart of the heating fluid before or after passing through the heataccumulator.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view in partly cross section showing a rotarytype regenerative heat exchanger according to a first embodiment of thepresent invention;

FIG. 2 is a view schematically showing the whole construction of aboiler and the rotary type regenerative heat exchanger according to thefirst embodiment of the present invention;

FIG. 3 is a view schematically showing the whole construction of aboiler and a rotary type regenerative heat exchanger according to asecond embodiment of the present invention;

FIG. 4 is a view schematically showing the whole construction of aboiler and a rotary type regenerative heat exchanger according to athird embodiment of the present invention;

FIG. 5 is a view schematically showing the whole construction of aboiler and a rotary type regenerative heat exchanger according to afourth embodiment of the present invention;

FIG. 6 is a perspective view in partly cross section showing aconventional rotary type regenerative heat exchanger; and

FIG. 7 is a view schematically showing the whole construction of aboiler and the conventional rotary type regenerative heat exchanger.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Embodiments of the present invention will be described below withreference to the accompanying drawings, that is, FIG. 1 to FIG. 5. Inthese drawings, like reference numerals are used to designate the samecomponents as those in the prior art, and their details are omitted.

First, a rotary type regenerative heat exchanger according to a firstembodiment of the present invention will be explained below withreference to FIG. 1 and FIG. 2. FIG. 1 is a perspective view in partlycross section showing a rotary type regenerative heat exchangeraccording to the present invention, and FIG. 2 is a view schematicallyshowing the whole construction of a boiler and a rotary typeregenerative heat exchanger according to the first embodiment of thepresent invention.

According to the first embodiment of the present invention, in order totake out a part of gas which is discharged from a rotary typeregenerative heat exchanger 40 and flows into a chimney stack (notshown), the rotary type regenerative heat exchanger 40 is provided witha branch pipe 41 at an outlet thereof. The branch pipe 41 is connectedwith a seal gas fan 42 for applying a pressure to the taken-out gas. Aseal gas pipe 44 is arranged on a downstream side of the seal gas fan42. Further, the seal gas pipe 44 is connected to a seal gas introducingduct 46 which is attached to the housing on the air side, and has oneend opening in a space between the rotor 4 and the housing 6 on the airside. In this case, a seal gas SG is pressurized by means of the sealgas fan 42, and then, is set to a value of the aforesaid inlet airpressure (Pai) or more.

Subsequently, an operation of the rotary type regenerative heatexchanger thus constructed according to the first embodiment will beexplained below. A part of gas, which is discharged from the rotary typeregenerative heat exchanger 40 and flows into a chimney stack (notshown), is taken out from the branch pipe 41 as a seal gas SG, and then,is pressurized to a value of the inlet air pressure (Pai) or more bymeans of the seal gas fan 42. The pressurized seal gas SG reaches theseal gas introducing duct 46 via the seal gas pipe 44, and then, isintroduced from the seal gas introducing duct 46 into a space surroundedby the rotor 4, the housing 6 on the air side, the bypass seal 26 andthe axial seal 28.

As a result, the pressure of the space becomes high; therefore, it ispossible to effectively prevent an air bypass leak ABL which hasconventionally generated. Further, since the air bypass leak ABL iseffectively prevented, a low temperature air A on the outlet does notmix with a high temperature air A on the outlet. Therefore, thetemperature of air A on the outlet becomes high, so that a heatefficiency of the boiler can be improved.

In this first embodiment, the seal gas SG introduced in the aforesaidspace flows into an air outlet side as a seal gas high temperature leakSGHL, and then, is mixed into the air A on the outlet. Since thetemperature of the seal gas SG at this time is higher than the inlet airtemperature, there is almost no influence of lowering the heatefficiency of the boiler 18 as compared with the conventional rotarytype regenerative heat exchanger in which the air bypass leak ABL isgenerated. Also, the seal gas axial leak SGAL is generated; however,this seal gas axial leak has no any influence on the heat efficiency ofthe boiler 18.

In the first embodiment, there is a need of additionally providing theseal gas fan 42 or the like as compared with the conventional rotarytype regenerative heat exchanger. However, the cost for providing theseal gas fan is extremely slight, and it is possible to improve a heatefficiency of the whole of steam power plant which comprises the boiler18 and the rotary type regenerative heat exchanger 40, as compared withthe conventional one.

Next, a rotary type regenerative heat exchanger according to a secondembodiment of the present invention will be explained below withreference to FIG. 3. FIG. 3 is a view schematically showing the wholeconstruction of a boiler and a rotary type regenerative heat exchangeraccording to the second embodiment of the present invention.

In this second embodiment, a branch pipe 47 is provided at an upstreamside from a position locating the rotary type regenerative heatexchanger 40 and a circulating gas fan 20, and then, branches and takesout a part of gas which is discharged from the boiler 18 and flows intothe rotary type regenerative heat exchanger 40. Further, the branch pipe47 is provided with a seal gas fan 48 for applying a pressure to thetaken-out gas. A seal gas pipe 50 is arranged on a downstream side ofthe seal gas fan 48. Further, the seal gas pipe 50 is connected to aseal gas introducing duct 46 which is attached to the housing 6 on theair side and has one end opening in a space between the rotor 4 and thehousing 6 on the air side. In this case, a seal gas SG is pressurized bymeans of the seal gas fan 48, and then, is set to a value of theaforesaid inlet air pressure (Pai) or more, like the above firstembodiment.

An operation of the rotary type regenerative heat exchanger thusconstructed according to the second embodiment will be explained below.A part of gas, which is discharged from the boiler 18, is taken out fromthe branch pipe 47 as a seal gas SG at an upstream side from a positionlocating a rotary type regenerative heat exchanger 40 and a circulatinggas fan 20, and then, is pressurized to a value of the inlet airpressure (Pai) or more by means of the seal gas fan 48. The pressurizedseal gas SG reaches the seal gas introducing duct 46 via the seal gaspipe 50, and then, is introduced from the seal gas introducing duct 46into a space surrounded by the rotor 4, the housing 6 on the air side,the bypass seal 26 and the axial seal 28.

As a result, the pressure of the space becomes high; therefore, it ispossible to effectively prevent an air bypass leak ABL which hasconventionally generated. Further, since the air bypass leak ABL iseffectively prevented, a low temperature air A on the inlet does not mixwith a high temperature air A on the outlet. Therefore, the temperatureof air A on the outlet becomes high, so that a heat efficiency of theboiler can be improved.

In this second embodiment, the seal gas SG is taken out from a hightemperature gas on the upstream side from the position locating therotary type regenerative heat exchanger 40 and the circulating gas fan20. Thus, there is almost no influence of lowering the heat efficiencyof the boiler 18.

Also, in the second embodiment, the seal gas SG introduced into theaforesaid space flows to the outlet side of air as a seal gas hightemperature leak SGHL, and then, is mixed into the air A on the outletside, like the above first embodiment. Since the temperature of the sealgas SG at this time is higher than the inlet air temperature, there isalmost no influence of lowering the heat efficiency of the boiler 18compared with the conventional rotary type regenerative heat exchangerin which an air bypass leak ABL has generated. Further, a seal gas axialleak SGAL is generated; however, the leak has no influence on the heatefficiency of the boiler 18.

Further, in this second embodiment, it is possible to improve a heatefficiency in the whole steam power plant which comprises the boiler 18and the rotary type regenerative heat exchanger 40 as compared with theconventional one, like the above first embodiment.

In this second embodiment, the pressure of the taken-out seal gas SG ishigher than the case of the first embodiment; therefore, it is possibleto make small a capacity of the seal gas fan 48.

Next, a rotary type regenerative heat exchanger according to a thirdembodiment of the present invention will be explained below withreference to FIG. 4. FIG. 4 is a view schematically showing the wholeconstruction of a boiler and a rotary type regenerative heat exchangeraccording to the third embodiment of the present invention.

In this third embodiment, the seal gas introducing duct provided in theabove first and second embodiments is provided on both the housing 6 onthe air side and the housing 6 on the gas side. More specifically, inthe third embodiment, a branch pipe 47 is provided at an upstream sidefrom a position locating the rotary type regenerative heat exchanger 40and the circulating gas fan 20, and then, branches and takes out a partof gas which is discharged from the boiler 18 and flows into the rotarytype regenerative heat exchanger 40. The branch pipe 47 is provided witha seal gas fan 48 for applying a pressure to the taken-out gas. A sealgas pipe 50 is arranged at a downstream side of the seal gas fan 48.Further, the seal gas pipe 50 is branched into a pipe 50 a and a pipe 50b. The pipe 50 a is connected to a seal gas introducing duct 46 which isattached to the housing 6 on the air side and has one end opening in aspace between the rotor 4 and the housing 6 on the air side. On theother hand, the pipe 50 b is connected to a seal gas introducing duct 46which has one end opening in a space between the rotor 4 and the housing6 on the gas side. In this case, the pipe 50 b is provided with apressure control valve 54. By the pressure control valve 54, thepressure of the seal gas SG introduced into the housing 6 on the gasside is controlled so as to become equal to the aforesaid inlet gaspressure (Pgi).

An operation of the rotary type regenerative heat exchanger thusconstructed according to the third embodiment will be explained below. Apart of gas, which is discharged from the boiler 18, is taken out fromthe branch pipe 47 as a seal gas SG at an upstream side from a positionlocating a rotary type regenerative heat exchanger 40 and a circulatinggas fan 20, and then, is pressurized to a value of the inlet airpressure (Pai) or more by means of the seal gas fan 48. One of thepressurized seal gas SG reaches the seal gas introducing duct 46provided on the housing 6 on the air side via the pipe seal gas pipe 50and the pipe 50 a, and then, is introduced from the seal gas introducingduct 46 into a space (first space) surrounded by the rotor 4, thehousing 6 on the air side, the bypass seal 26 and the axial seal 28.Meanwhile the other of the pressurized seal gas SG is supplied via theseal gas pipe 50 and the pipe 50 b, and then, is controlled by means ofthe pressure control valve 54 so that the pressure seal gas SG becomesequal to an inlet gas pressure (Pgi). Thereafter, the pressurized sealgas SG reaches a seal gas introducing duct 52 provided at the housing 6on the gas side, and then, is introduced from the seal gas introducingduct 52 into a space (second space) surrounded by the rotor 4, thehousing 6 on the gas side, the bypass seal 26 and the axial seal 28.

As a result, the pressure of the aforesaid first space becomes high;therefore, it is possible to effectively prevent an air bypass leak ABLwhich has conventionally generated. Further, since the air bypass leakABL is effectively prevented, a low temperature air A on the inlet doesnot mix with a high temperature air A on the outlet. Therefore, thetemperature of air A on the outlet becomes high, so that a heatefficiency of the boiler can be improved. Moreover, in this thirdembodiment, the pressure of the aforesaid second space becomes high;therefore, it is possible to effectively prevent a gas bypass leak GBLwhich has conventionally generated. Further, since the gas bypass leakGBL is effectively prevented, the quantity of gas contributing to heatexchange increase as compared with the cases of the first and secondembodiments, so that the heat efficiency of the boiler 18 can beimproved.

Also, in this third embodiment, like the above first and secondembodiments, the seal gas SG in the aforesaid first space flows into theair outlet side as a seal gas high temperature leak SGHL in the housing6 on the air side, and then, is mixed into the outlet air A. However,the temperature of the gas seal SG at this time is higher than the inletair temperature; therefore, there is almost no influence of lowering theheat efficiency of the boiler 18 as compared with the conventionalrotary type regenerative heat exchanger in which the air bypass leak ABLhas generated. Although the seal gas axial leak SGAL is generated, thisleak has no influence on the heat efficiency of the boiler 18. Meanwhilethe seal gas SG in the aforesaid second space flows into the gas outletside as a seal gas low temperature leak SGLL in the housing 6 on the gasside, and then, is mixed into the outlet gas G, and thereafter, isdischarged from the chimney stack.

Also, in this third embodiment, it is possible to improve a heatefficiency of the whole steam power plant which comprises the boiler 18and the rotary type regenerative heat exchanger 40 as compared with theconventional one, like the above first and second embodiments.

Thus, in the third embodiment, it is possible to prevent both air bypassleak ABL and gas bypass leak GBL, so that the heat efficiency of theboiler 18 can be further greatly improved as compared with the abovefirst and second embodiments.

Next, a rotary type regenerative heat exchanger according to a fourthembodiment of the present invention will be explained below withreference to FIG. 5. FIG. 5 is a view schematically showing the wholeconstruction of a boiler and a rotary type regenerative heat exchangeraccording to the fourth embodiment of the present invention. In thisfourth embodiment, the construction is basically the same as theaforesaid third embodiment except the following matters. Morespecifically, in this fourth embodiment, in order to take out a part ofgas, a branch pipe 51 and a seal gas fan 56 are provided at a downstreamside from the circulating gas fan 20. As a result, the taken-out gas isalready pressurized to some degree by means of the circulating gas fan20, so that the capacity of the seal gas fan 56 can be made small ascompared with that of the third embodiment.

Many other variations and modifications of the invention will beapparent to those skilled in the art without departing from the spiritand scope of the invention. The above-described embodiments are,therefore, intended to be merely exemplary, and all such variations andmodifications are intended to be included within the scope of theinvention as defined in the appended claims.

The disclosure of Japanese Patent Application No.9-349876 filed on Dec.19, 1997 including specification, claims, drawings and summary areincorporated herein by reference in its entirety.

What is claimed is:
 1. A rotary type regenerative heat exchangercomprising: a rotor rotating around a central shaft; a heat accumulatorwhich is constructed in a manner that a heated fluid and a heating fluidfilled in the rotor alternately pass therethrough by a rotation of therotor to repeat heat accumulation and radiation; a housing provided soas to house the rotor; take-out means for taking out a part of theheating fluid; pressurizing means for pressurizing the taken-out heatingfluid to a predetermined pressure; and a pressurized fluid introducingpassage which is provided in the housing so as to introduce thepressurized heating fluid into a predetermined space formed between therotor and the housing.
 2. The rotary type regenerative heat exchangeraccording to claim 1, wherein said pressurized fluid introducing passageis provided on the heated fluid side of the housing, the heating fluidside of the housing, or on both heated fluid side and heating fluid sideof the housing.
 3. The rotary type regenerative heat exchanger accordingto claim 1, wherein said take-out means branches and takes out a part ofthe heating fluid before or after passing through the heat accumulator.4. The rotary type regenerative heat exchanger according to claim 2,wherein said take-out means branches and takes out a part of the heatingfluid before or after passing through the heat accumulator.
 5. Therotary type regenerative heat exchanger according to claim 1, whereinsaid take-out means branches and takes out a part of gas at a downstreamside from a circulating gas fan which returns a part of the gasdischarged from a boiler to the boiler as a re-circulating gas again. 6.The rotary type regenerative heat exchanger according to claim 2,wherein said take-out means branches and takes out a part of gas at adownstream side from a circulating gas fan which returns a part of thegas discharged from a boiler to the boiler as a re-circulating gasagain.